1. Field of the Invention
The present invention relates in general to a novel device for supporting conductors, and more particularly to a novel device for supporting a plurality of parallel conductors, and each conductor being insulated from the other conductors. The invention also relates to an insulating support and more particularly to an insulating support which is used in a device for supporting conductors.
2. Description of the Prior Art
Currently the amount of electric energy used is becoming larger and larger. Thus, the size of the conductors of the main bus bars in, for example, a metal-enclosed switchgear, has necessarily been increased. In this situation the shock due to the electromagnetic force applied to the conductors becomes large when the main bus bars are short-circuited. Therefore, the device for supporting the conductors and the insulating supports are required to be sufficiently strong to endure this shock. As a result of this requirement, the amount of insulating material used in the insulating supports becomes large.
Hereinafter, a device for supporting conductors used in a metal-enclosed switchgear will be explained as an example. FIG. 1 shows a commonly used metal-enclosed switchgear and FIG. 2 shows a device for supporting conductors in the metal-enclosed switchgear in FIG. 1. In FIG. 1 and FIG. 2 three parallel conductors 1A, 1B, and 1C are shown which correspond to a three phase run. Insulating supports 3, each including a threaded bore hole 2 at each end, are inserted between the conductors 1A, 1B, 1C and between the outer conductors 1A, 1C and bracket hardware 5. A bolt 7 is inserted into each of the outer insulating supports 3 through a through-hole, not shown, in the bracket hardware 5 and is screwed into the threaded bore hole 2 in the outer insulating support 3. A stud 6 having a threaded terminal at each end thereof is inserted into the insulating supports 3 which are adjacent to each other through throughholes 4 in the conductors 1A, 1B, 1C. Each threaded terminal portion of this stud 6 is screwed into one of the threaded bore holes 2 in the insulating supports 3.
The device for supporting conductors is constructed as explained above, so very large compressive forces or tensile forces are applied to the insulating support 3 by the electromagnetic force applied to the conductors 1A, 1B, 1C when the main bus bars are short-circuited. As the insulating support 3 is made of insulating material, it exhibits lower strength to tensile forces than to compressive forces. Therefore, in order to endure large electromagnetic forces, the cross-section of the insulating support 3 must be large and the threaded bore holes 2 of the insulating support 3 must be constructed to increase the friction force at the threaded bore holes 2. Thus each insulating support 3 must be made very large and the insulating material used in each insulating support 3 must be strong. As a result, the weight of each insulating support 3 and the apparatus for supporting the insulating supports become large. Also, much precision is required to make the threaded bore holes in the insulating support 3, thereby requiring much time and expense. If the stud 6 is too long in relation to the depth of this threaded bore hole, the conductors will not be sufficiently supported, so the length of the stud 6 must be controlled precisely. Also, it is necessary to screw the stud 6 equally into each threaded bore hole 2 of the insulating supports 3. As explained above, its takes a lot of time and expense to assemble the prior art device for supporting conductors. Moreover, the gap between the conductors 1A, 1B, 1C changes according to the lay out of the conductors and the rating current of the conductors, so insulating supports of varying length are required. Thus, various sized molds for forming the various sized insulating supports are required. As a result, the cost of making the insulating support 3 becomes large. The prior art devices for supporting conductors and insulating supports have the defects described above.